Effects of Sedation by Intramuscular Administration of Medetomidine on Canine Abdominal Vascular System and Hepatic Parenchyma Imaging Using Enhancement Dynamic Computed Tomography

Kenji Kutara,Yoshiki Itoh,Noritaka Maeta,Fumiko Ono,Teppei Kanda,Taketoshi Asanuma,Yohei Mochizuki

doi:10.3390/vetsci7030091

Abstract

This prospective crossover study compared the effects of intramuscular administration of medetomidine for sedation on parameters of the abdominal vascular system, measured by enhancement computed tomography (CT), to those of propofol-induced sevoflurane maintenance anesthesia, as a control, in five clinically healthy adult male beagle dogs (11.4–12.8 kg). Each animal underwent both protocols at a 1-week interval. The enhancement (HU) and time to peak enhancement on CT were measured for the aorta (AO), caudal vena cava (CVC), portal vein (PV), and hepatic parenchyma (HP). The contrast effects in the AO, PV, and HP were significantly delayed under medetomidine sedation compared to the control anesthesia protocol. Particularly, the contrast effect in the PV and HP was significantly delayed under sedation, appearing approximately 1 min after contrast medium injection. This delay likely reflects the peripheral vasoconstrictive effect of medetomidine. We noted a generally early high contrast enhancement of the CVC under medetomidine sedation, likely contributed by the induced bradycardia. Therefore, findings obtained on contrast enhancement CT under medetomidine sedation may be different from those obtained under propofol-induced sevoflurane maintenance anesthesia. These differences are important to consider when using the findings to inform diagnosis.

Highlights

In veterinary medicine, multiphasic multi-detector computed tomography (CT) angiography, including triple-phase helical CT, is currently used as a diagnostic tool for vascular disorders, such as portosystemic shunts [1], arteriovenous fistulae [2], and various tumors [3,4,5,6,7,8]
There was no characteristic change in heart rate (Table 3), all blood pressure values were significantly lower at the start time of scanning than before anesthesia (Table 4)
We propose that the large delay in the contrast effect in the portal vein (PV) and hepatic parenchyma (HP) compared to that in the AO with the sedation protocol might be caused by medetomidine-induced peripheral vasoconstriction, as well as by bradycardia

Summary

Introduction

Multiphasic multi-detector computed tomography (CT) angiography, including triple-phase helical CT, is currently used as a diagnostic tool for vascular disorders, such as portosystemic shunts [1], arteriovenous fistulae [2], and various tumors [3,4,5,6,7,8] This method is commonly used for characterizing parenchymal disease, such as pancreatic disease [9,10,11,12]. For triplephase helical CT, a single bolus injection of contrast medium enhances imaging during the phase of preferential arterial enhancement, followed by the portal venous phase, and the delayed phase [5,6].

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